ProtoprioniodusProtoprioniodus is an extinct genus of conodonts.Use in stratigraphyThe Whiterock Stage refers mainly to the early Middle Ordovician in North America. It is often used in the older literature in a global sense. The Whiterock Stage is given a range from 471.8 to 462 m.y.a., spanning close to 10 million years. Officially its start is defined by the potentially lowest occurrence of the conodonts Protoprioniodus aranda or Baltoniodus triangularis.